The present, invention is related to a method and an apparatus for arranging balls in a ball bearing, specifically to a method and an apparatus for arranging a plurality of balls circumferentially with a uniform interval (uniform space) before the step of mounting a retainer in assembling the ball bearing.
In assembling a ball hearing comprising an inner ring 1 and an outer ring 2, at first, as shown in FIG. 7 (A), a plurality of balls 3 are installed in an annular space 4 between an inner ring raceway in the outer peripheral surface of the inner ring 1 and an outer ring raceway on the inner peripheral surface of the outer ring 2, and a plurality of the balls 3 are arranged circumferentially with a uniform interval therebetween as shown in FIG. 7 (B). Next, an annular retainer (not shown) is pushed in the annular space 4 between the inner ring raceway and the outer ring raceway so as to rotatably retain the balls 3.
When the plurality of the balls 3, installed and arranged with uneven spaces in the annular space 4 as shown in FIG. 7 (A), are arranged with the uniform interval, as shown in FIG. 7 (B), the force of the hydraulic fluid is utilized to circumferentially move each of the balls 3 while preventing the rolling surface of each of the balls 3 from being injured, which is conventionally known, for examples, in Japanese Patent Publications No. Toku Kai Hei 05-104361, or No. Toku Kai Hei 05-104362.
FIGS. 8 (A) to 8 (C) show the first example of the invention described in Japanese Patent Publication No. Toku Kai Hei 05-104362. A compressor is used to supply the compressed air, one kind of pressurized fluid, to a nozzle device 7 comprising an annular manifold 5 (refer to FIG. 10 described below, omitted in FIGS. 8(A) to 8(C)) which is connected to the discharge opening of the compressor, and nozzles 6 which are provided on one surface of the manifold 5 circumferentially with a uniform interval. The number (sixteen in the example shown) of the nozzles 6 is twice the number of the balls 3 to be arranged (eight in the example shown). Valve devices (not shown), which are electromagnetically opened and closed, are provided in the air paths communicated with the nozzles 6, respectively, and signals produced by a controller (not shown) are used to independently open and close each of the valve devices.
With the nozzle device 7 constructed as mentioned above, the balls 3 existing with uneven spaces between the outer peripheral surface of the inner ring and the inner peripheral surface of the outer ring as shown in FIG. 8 (A), are arranged with a uniform interval in the circumferential direction, as shown in FIG. 8 (C), through the steps as described below.
At first, as shown in FIG. 7 (A), the balls 3 are inserted between the inner ring raceway provided on the outer peripheral surface of the inner ring 1 and the outer ring raceway provided on the inner peripheral surface of the outer ring 2. This inserting operation is conducted in the condition that the centers of the inner ring 1 and the outer ring 2 are displaced from each other, and the width of the annular space 4 between the outer peripheral surface of the inner ring 1 and the inner peripheral surface of the outer ring 2 is increased at one circumferential portion. Accordingly, the balls 3, immediately after installed, are concentrated at the one circumferential portion. In this condition, the nozzle device 7 is placed axially beside the inner ring 1 and the outer ring 2, so that the nozzles 6 face the annular space 4 (refer to FIG. 7 (A)) between the inner ring raceway and the outer ring raceway.
Next, shown in FIG. 8 (B), by spouting the compressed air from one or some of the nozzles 6, the balls 3 are moved in the circumferential direction, so that the balls 3, are arranged circumferentially with a uniform interval as shown in FIG. 8 (C). That is to say, as shown in FIG. 9, when spouting the compressed air to one of the balls 3 from one of the nozzles 6, as clear in the Bernoulli""s theory, pressure (the static pressure) acts onto the either side of the ball 3, such that it is low on the side where the nozzle 6 exists and the stream is swift, and high on the opposite side. Accordingly, the ball 3 is drawn toward the center axis of the nozzle 6. And, after the center of this ball 3 has moved on the extension line (center axis) of the nozzle 6, as long as the compressed air continues spouting from the nozzle 6, the ball 3 is sustained in the position facing the nozzle 6.
Accordingly, by proper switching between on and off in spouting the compressed air from the sixteen nozzles 6 provided in the manifold 5, the eight balls 3 are moved in the circumferential direction, so that the balls 3 are placed at the respective positions facing the respective alternate eight nozzles 6. Then the eight balls 3 are arranged circumferentially with a uniform interval.
Next, FIG. 10 shows the second example of the prior art method described in the publication. Although, in the first example shown above, the number (sixteen) of the nozzles 6 in the nozzle device 7 is twice the number (eight) of balls 3 to be arranged, in this example, the number of the nozzles 6 in the nozzle device 7a is equal to the number (eight) of the balls 3. Instead, the manifold 5, which forms the nozzle device 7a together with the nozzles 6, is rotatable in either of the circumferential directions, as shown by the arrow xe2x80x98Xxe2x80x99 in FIG. 10.
In the case of arranging the balls 3 circumferentially with a uniform interval by the second example method using the nozzle device 7a, the compressed air is spouted from one or some of the plurality of the nozzles 6, while the manifold 5 is rotated in the circumferential direction, clockwise and counterclockwise, so that every ball 3 is retained in the position facing each of the eight nozzles 6. In this case, by properly regulating the speed and the angle of rocking of the manifold 5, it is prevented that two or more balls 3 are kept to be attracted to one nozzle 6. That is, the extra balls 3 are shaken off.
Moreover, as a method for the purpose of the more smooth operation for arranging a plurality of balls by compressed fluid, Japanese Patent Publication No. Toku Kai Hei 07-290329 (US 5,678,310) disclosed a method using the apparatus as shown in FIG. 11 or FIG. 12. With the third and fourth examples described as prior art methods in this publication, in the third example using the apparatus as shown in FIG. 11, a positioning land 9 is formed at the upper center portion of a mounting block 8 functioning as the manifold, and the inner ring 1 is fitted without play onto the positioning land 9. Then, the compressed air, or the pressurized fluid is spouted out of the upper opening of each of the nozzles 6 around this positioning land 9 to the annular space 4 existing between the outer peripheral surface of the inner ring 1 and the inner peripheral surface of the outer ring 2. The number of the nozzles 6 is the same to that of the balls 3.
Further, in this example, no special device such as electromagnetic valve is provided between each of the nozzles 6 and the air supplying path 11 communicated with the source of the compressed air, such as the compressor 10. Consequently, while opening the electromagnetic valve, not shown, which is provided between the air tank attached to the compressor 10 and the air supplying path 11, the same amount of the compressed air is spouted at the same velocity from each of the nozzles 6.
And, above the upper opening of the annular space 4, a rod 14 is hung, and a disturbance plate 12 is connected to the lower end of the rod 14. The annular disturbance plate 12 is provided, so that the sloped lower surface 13 of this disturbance plate 12 faces to the upper end opening of the annular space 4. The disturbance plate 12 can freely rise, descend, rotate and rock. Consequently, the distance between the lower surface 13 of the disturbance plate 12 and the upper end of the inner ring 1 and the outer ring 2 is freely altered with respect to the circumferential direction.
Utilizing the apparatus as described above, the operation of circumferentially arranging the balls 3, just inserted into the annular space 4, with a uniform interval are conducted as follows.
At first, as shown in FIG. 7 (A) explained above, the ball bearing having the balls 3 arranged into the annular space 4 with uneven spaces is mounted onto the upper surface of the mounting block 8 as shown in FIG. 11. Then, while compressed air is spouted from the nozzles 6, the disturbance plate 12 is moved in the proper direction.
While spouting the compressed air from the nozzles 6, by moving the disturbance plate 12, that is by making the disturbance plate 12 rotate, rise, descend and rock, the balls 3 existing in the annular space 4 in a cluster state can be separated from each other. For example, as shown in FIG. 13, when three balls 3 are caught by a pair of nozzles 6 adjacent to each other, by making the disturbance plate 12 rotate, rise, descend and rock, one part of the lower surface 13 comes closer to the balls 3, and the stream of the pressurized air spouted from the pair of nozzles 6 is disturbed, so that the three balls 3 are separated from each other. Accordingly, like the first and second examples in the prior art method shown in FIGS. 8 thru 10 mentioned above, each of the nozzles 6, individually retains one of the balls 3.
Next, in the case of the fourth example of the prior art method using the apparatus shown in FIG. 12, at the lower surface 13 of the disturbance plate 12, a plurality of third nozzles 15 are provided. The number of the nozzles 15 may not be the same to that of the balls 3 to be arranged, and the nozzles 15 may not be provided circumferentially with a uniform interval. In order to arrange the balls 3, just inserted in the annular space 4, circumferentially with a uniform interval, at the same time when or, after or before spouting the compressed air from each of the nozzles 6, compressed air is spouted from each of the nozzles 15. And, as necessary, the disturbance plate 12 is made to rotate, rise, descend and rock. Consequently, the operation of separating the balls 3 which are close to each other is efficiently conducted.
In the case of the prior art method described above, as shown in FIG. 13, a long time of operation is required in separating certainly the three or more balls 3 which are provided close to each other, and arranging them with the uniform space. Consequently, in order certainly to arrange three or more balls 3 with a uniform interval in the automatic assembling process, the continuing time of spouting the compressed air must be long. As a result, the assembling efficiency of the ball bearing decreases, and moreover the consumption of the compressed air increases, which causes the higher cost of assembling the ball bearing.
On the other hand, shortening the continuing time would make high the possibility of the balls 3 entering the next retainer assembling process before they are arranged with a uniform interval, which would make high the trouble occurrence frequency in this process, and therefore could not be adopted. Specifically, even if the trouble frequency is very low, the trouble, once occurred, would make the producing efficiency remarkably worse in the mass-production, and therefore the trouble frequency needs to be as nearly zero as possible. At this respect, the prior art method mentioned above must still be improved.
Concerning the cause of the trouble occurrence mentioned above, the present inventors considered as follows: That is to say, with every prior art method, the inner ring 1 and the outer ring 2 for the ball bearing are placed together on the same mounting block 8. Consequently, in the operation of arranging the balls 3 with a uniform interval, the position relationship of the inner ring 1 and the outer ring 2 is not changed. On the other hand, in order to conduct this process, when mounting the ball bearing on the mounting block 8, the position relationship between the inner ring 1 and the outer ring 2 is slightly changed, and the space between the inner ring raceway provided on the outer peripheral surface of the inner ring 1 and the outer ring raceway provided on the inner peripheral surface of the outer ring 2, may be narrower at one portion of the circumferential direction, although slightly. Consequently, at the narrower portion like this, the frictional force acting at the contact position between each of the raceways and the rolling surface of the balls 3 increases. As a result, in the narrower space portion between the raceways, as mentioned above, three or more balls 3 are inclined to get together as shown at the lower left portion and the upper right portion in FIG. 13, and they are not easily separated.
The method of arranging the balls circumferentially with a uniform interval by using the pressurized fluid, other than in the two publications mentioned above, is disclosed in Japanese Patent Publications Nos. Toku Kai Hei 05-104361, 11-99419 or 11-153139 are known. Among them, the method described in Japanese Patent Publication No. Toku Kai Hei 11-99419 is substantially the same to the method described in No. Toku Kai Hei 07-290329 (US 5,678,310) mentioned above and has the same problem. And with the method described in No. Toku Kai Hei 05-104361, in the operation of arranging the balls circumferentially with a uniform interval, the balls are left under the condition that the preload is applied to them based on the weight of the inner ring. Consequently, the surface pressure at the contact portion between the rolling surface of each of the balls and the inner and outer ring raceways correspondingly increases, then the balls are hardly separated in the circumferential direction of the raceways.
Further, in the case of the method described in Japanese Patent Publication No. Toku Kai Hei 11-153139, as the downstream end of the nozzle is formed in a two-tip-fork or a horn shape, the force based on the dynamic force of the compressed air spouted from the downstream end has a component of force in circumferential direction. However, in the case of the method described in Publication No. Toku Kai Hei 11-153139, as the shape of the downstream end of the nozzle is symmetrical with respect to the circumferential direction, depending on the position relationship between the balls close to each other and the nozzles, the balls may be hardly separated.
In viewing such circumstances, this invention was attempted to realize the method and apparatus for positively arranging a plurality of balls with a uniform interval in a short time.
An object of the present invention is to provide a method and an apparatus for arranging a plurality of balls in a ball bearing circumferentially with a uniform interval without injuring the balls, wherein an inner ring and an outer ring of the ball bearing are independently mounted to an inner ring mounting block and an outer ring mounting block, respectively, and pressurized air is spouted from a plurality of nozzles, such that by the force of this pressurized air, the balls are moved to face the nozzles, respectively.